I. Field of the Invention
This invention relates generally to digital telecommunication systems and more specifically to a system for transmitting radar data and related alphanumeric and graphic information from one or more radar installations to a plurality of remote receiver locations via voice grade phone lines, thereby allowing weather information being sensed by the National Weather Bureau (NWB) radars, to be made available at TV stations, airline operations facilities or other sites where up-to-the-minute, real-time information on weather conditions existing at any number of geographic locations may be needed.
II. Discussion of the Prior Art
The National Weather Service maintains a network of radar installations in the United States which provide complete overlapping coverage of the portion of the United States which lie east of the Rocky Mountains. At the time of this writing, this network is comprised of 51 WSR-57S radars and 5 WSR-74S radars which operate 24 hours a day, 365 days a year. These radar installations make hourly observations around the clock and, based upon the observations, teletyped messages relating to observed precipitation are disseminated to subscribers. In addition to the foregoing network, the National Weather Service also operates a secondary or Local Warning Radar network which is comprised of approximately 60 WSR-74C radars which are brought into play when severe weather threatens.
In addition to providing teletype communication to subscribers of previously formatted weather information obtained from the radar equipment, the National Weather Service also has installed the Weather Bureau Radar Remote (WBRR) equipment on 37 sites, this equipment being designed to provide annotated plan position indicator (PPI) display at locations remote from the radar sites. A camera is made to scan at a slow rate so that the generated information bits defining the picture can be transmitted over telephone lines, thus avoiding the expense of coaxial cable or a microwave transmission link. Using this system, it is possible to dial a transmitting site via a phone connection and obtain a transmission of the picture information from any of the radar locations which are suitably equipped with equipment to accommodate this function. Not only is the WBRR complex used by the National Weather Service, but it also is utilized by private meteorologists, airlines, television stations and other Government agencies. In implementing this system, a PPI display is slaved off of the usual radar receiver and this slave display utilizes a high persistency phosphor for prolonged image retention. A facsimile type scanner monitors the slave and develops picture information which may be transmitted over the phone lines to the receiving site where the image is replicated on a paper medium and may include alphanumeric and graphic information.
Further information relating to the WBRR system may be obtained from a publication entitled "Introduction to Weather Radar" published in August 1979 by the U.S. Department of Commerce, National Oceanic and Atmospheric Administration. In addition to describing that system, this publication further provides useful background information relating to the NWS Digital Video Integrator and Processor more commonly referred to by the acronym D-VIP. The D-VIP is a device which automatically processes the output of the radar's receiver to produce up to six levels of intensity data corresponding to preselected categories of estimated rainfall rates measured in inches per hour and ranging from 0 precipitation to an extreme intensity wherein the precipitation is greater than 7.1 inches per hour. These levels may be displayed individually or simultaneously on a radar scope. The D-VIP operates substantially continuously and may be used to display a contoured picture of a weather cell in a single sweep of the radar antenna.
The system of the present invention is a marked improvement over the prior art WBRR equipment. Basically, the present invention comprises a transmitter unit located usually proximate to the NWS weather radar console and a plurality of dispersed receiver units which are preferably coupled to the transmitter by way of either dedicated or dial-up telephone lines. Contained within the transmitter module is a digital computer programmed to transmit over the telephone lines, a four-range radar image along with corresponding map overlays to any of the plural remote receivers interrogating the transmitter at the radar site. The computer is adapted to process the radar video and azimuth information into a multi-range format and must convert, on a real-time basis, the polar coordinate data produced by the video and azimuth inputs into a rectangular format compatible with the conventional raster scan used on most television display screens. In addition, the computer is capable of storing the high speed data into its memory while simultaneously overseeing the transmission of data over the phone lines to the calling receiver module. That is to say, the computer also acts as a communications processor, performing the task of sending the converted digital data via a modulator section contained in the transmitter module to the phone line interface.
The data transmitted over the phone line is in a multi-range format made possible by the concurrent interaction between the transmitter's computer and the communications processor. The transmitter module of the system of the present invention is further designed to sample the D-VIP data and to transmit the various precip levels to the receiver site.
The system's receiver modules each comprise a receive-only, multi-function, color, graphics terminal which is capable of interrogating a transmitter by way of a "dial-up" operation and to process received data so that it may be presented on a conventional raster scan display or transmitted via commercial TV networks. Included within the receiver are four memory banks for temporarily storing radar information relating to the four ranges, whereby the individual and instantaneous display, in a six-color format representing the predetermined precipitation intensity levels obtained by the transmitter from the NWS D-VIP equipment can be displayed.
The receiver module further includes suitable controls and circuitry whereby any quadrant of the screen presentation at any range can be expanded to fill the entire screen. Push button controls allow for instantaneous display of the four ranges. The data displayed further includes pertinent geographic features (map information) encoded into the data at the transmitting site and sent over the phone lines to the receiver module. Further control switches permit an operator to display any one or more levels of precipitation in differin colors or in a blinking fashion for ease of identification of critical conditions. Several additional features are also incorporated for enhancing to flexibility of the system and these additional features are set out fully herein.
Hence, the present invention constitutes a significantimprovement over known prior art arrangements for receiving radar information from a radar receiver, formatting the information for economical transmission to remote receiver sites via low band-width, voice grade telephone lines where the data may be reconstructed and reconstituted for further use or transmission via conventional television station apparatus.